The invention relates to a thyristor whose semiconductor body includes a sequence of at least four layer-like zones of alternatingly opposite conductivity type and an emitter zone which at least in part encloses the control electrode and is provided with channeling for the penetration of the adjacent base zone to the emitter electrode.
In thyristors having so-called shorted emitters, the base zone, which is provided with the control electrode, penetrates to their common surfacae through channeling in the adjacent emitter zone and the parts of the base zone passing through the emitter zone are electrically contacted together via the emitter electrode and short-circuit the emitter zone. If a blocking voltage of great steepness occurs across the thyristor, the capacitive effect of the blocking pn-junction causes part of the shifting current to flow through the penetrations directly into the emitter electrode. This reduces the injection effect of the emitter zone into the adjacent base zone so that, with a corresponding penetration density, firing of the thyristor is prevented.
In known thyristor embodiments, the penetrations are arranged in a square, hexagonal, radial or involute-shaped pattern. Thus German Patent No. 2,123,322 discloses the provision of penetrations on lines which radially emanate from the control electrode. In order to realize a certain minimum penetration density over the emitter area, additional penetrations are provided on the angle bisector between adjacent radii where the latter are further apart from one another. Such an arrangement, however, does not exhibit the uniform penetration density required for optimization of the dv/dt behavior.
Particularly when the circular control electrode, which is advantageous for the operation of a thyristor, is disposed in the center of the one major surface, some of the prior art penetration patterns exhibit the drawbacks of uneven spacing, differences in density as well as insufficient firing propagation.
Additionally, German Patent No. 2,438,894 discloses a thyristor with shorted emitte where the shorts have a diameter equal to or less than 20 .mu. and wherein the ratio of the distance between two adjacent shorts to their diameter is greater than or equal to three. Since either value of the ratio, and thus the ratio itself, is selectable, the disclosed dimensioning rule does not provide a teaching as to how optimization of the dv/dt behavior as well as the firing propagation can be realized with a pattern for arranging the penetrations particularly in the region near the control electrode.